Justin Bieber

Arresting DUI Officer Has Big Credibility Problems

2/20/2014 12:45 AM PST BY TMZ STAFF

EXCLUSIVE

The Miami Beach cop who claimed he stopped Justin Bieber last month because he was drag racing has been called on the carpet numerous times for misconduct ... TMZ has learned.

Officer Steven Cosner wrote in his police report he observed cars driven by Bieber and Khalil in the middle of a drag race -- at speeds between 55 and 60 MPH. TMZ broke the story ... the GPS tracking system shows in the middle of the so-called drag race, the maximum speed of the cars was 27 MPH.

We're told Bieber's legal eagles believe Cosner is lying, and now they have some firepower.

TMZ has obtained numerous Miami Beach PD internal affairs documents, which show Cosner has been accused of misconduct 15 times -- from 2001 to 2012. Of those, Cosner failed to show up for court hearings 5 times. In each case he was reprimanded -- 3 verbal warnings and 2 write-ups.

Our sources say ... Bieber's lawyer will raise the issue ... Cosner may not have shown up for court because he may not have wanted to be placed under oath. In other words, if you lie under oath you can be prosecuted for perjury.

On another occasion in 2006 the PD says he committed 3 offenses -- violating the rules of "courtesy and respect," "Off duty/secondary employment," and "unlawful compensation." For those violations he was suspended.

In 2007 Cosner was accused of offensive conduct/language. For some reason the allegation seems to still be "open" in that case.

And in 2011 Cosner was written up for sleeping on duty.

As for the remaining 7 cases ...Cosner was exonerated by Internal Affairs.

Cosner's record could create problems for prosecutors if the DUI case goes to trial.